Technical Field
The present invention relates to a pouch-shaped secondary battery including a micro-perforated electrode lead having adhesive properties, and more particularly to a pouch-shaped secondary battery including a micro-perforated electrode lead having adhesive properties that is capable of enabling a short circuit to occur in the pouch-shaped secondary battery using the adhesive properties of the micro-perforated electrode lead with respect to a pouch-shaped battery case in order to secure the safety of the pouch-shaped secondary battery when the pouch-shaped secondary battery swells due to gas generated in the pouch-shaped secondary battery while the pouch-shaped secondary battery is in an abnormal state or when the pouch-shaped secondary battery is overcharged.
Discussion of the Related Art
In general, there are various kinds of secondary batteries, such as a nickel cadmium battery, a nickel hydride battery, a lithium ion battery, and a lithium ion polymer battery. Such secondary batteries have been used in large-sized products that require high output, such as an electric vehicle and a hybrid electric vehicle, a power storage device for storing surplus power or new and renewable energy, and a backup power storage device, as well as small-sized products, such as a digital camera, a portable digital versatile disc (DVD) player, an MP3 player, a personal digital assistant (PDP), a portable game device, a power tool, and an electric bicycle (E-bike).
A lithium secondary battery generally includes a positive electrode, a separator, and a negative electrode. The materials of the positive electrode, the separator, and the negative electrode are selected in consideration of the lifespan, the charge and discharge capacity, the temperature characteristics, and the safety of the lithium secondary battery. In general, the lithium secondary battery is configured to have a three-layered structure, in which a positive electrode, a separator, and a negative electrode are sequentially stacked. Alternatively, the lithium secondary battery is configured to have a five-layered structure, in which a positive electrode, a separator, a negative electrode, a separator, and a positive electrode are sequentially stacked, or to have another five-layered structure, in which a negative electrode, a separator, a positive electrode, a separator, and a negative electrode are sequentially stacked.
A lithium secondary battery is charged and discharged through a process in which lithium ions from a lithium metal oxide of a positive electrode are repeatedly intercalated into a negative electrode, such as a graphite electrode, and the lithium ions are repeatedly deintercalated from the negative electrode.
Heat may be generated from such a lithium secondary battery due to a short circuit occurring in the lithium secondary battery due to external impacts, overcharge of the lithium secondary battery, or overdischarge of the lithium secondary battery. As a result, an electrolyte may be decomposed in the lithium secondary battery, and thermal runaway occurs in the lithium secondary battery. That is, the safety of the lithium secondary battery is threatened in several aspects. In particular, the secondary battery may explode for various reasons. In one example, the secondary battery may explode due to an increase in the pressure of the air in the secondary battery, which is caused by the decomposition of an electrolyte. Specifically, when the secondary battery is repeatedly charged and discharged, gas may be generated in the secondary battery as the result of the electrochemical reaction between the electrolyte and an electrode active material. The gas generated in the secondary battery increases the pressure in the secondary battery. As a result, the fastening force between parts constituting the secondary battery may be reduced, the external case of the secondary battery may be damaged, a protection circuit of the secondary battery may be operated early, an electrode of the secondary battery may be deformed, a short circuit may occur in the secondary battery, or the secondary battery may explode.
In order to secure the safety of such a battery when the battery is overcharged, overcurrent is prevented from flowing in the battery through the control of electronic parts, whereby the battery is prevented from being overcharged. To this end, a protection circuit, such as a protection circuit module (PCM), may be applied to the battery. Even in the case in which such an overcharge protection circuit, such as a PCM, is applied to the battery, however, it is difficult to sufficiently secure the safety of the battery. In particular, it is necessary for a pouch-shaped battery to be provided with a further improved protection circuit structure in order to more accurately check the swelling of the pouch-shaped battery.
In addition, there has been used a mechanical current interrupt device (CID) that physically interrupts the series connection of a battery pack using the pressure generated in the battery due to thermal expansion of the battery when the battery is overcharged in consideration of malfunction of the electronic parts of the battery. Generally, in the current interrupt device of the battery pack, there is widely used a method of physically cutting the series connection of the battery pack through the structure of the battery pack using only the pressure generated in the battery as the battery is expanded when the battery is overcharged in order to interrupt the flow of current in the battery pack. However, a current interrupt device (CID) that is capable of interrupting the flow of current in a pouch-shaped battery without using an additional component when the volume of the pouch-shaped battery is increased has not been suggested.
Korean Registered Patent No. 1601135 discloses a pouch-shaped secondary battery configured to have a structure in which two lead plates are coupled to each other via a polymer material interposed between the lead plates, in which a vent notch is provided in order to rapidly discharge gas, generated in the secondary battery, out of the secondary battery when the pressure in the secondary battery reaches a predetermined level due to the gas, and in which first and second sealants, which are interposed between the lead plates, exhibit electrical insulation and thermal fusion properties. However, a structure in which a conductive polymer is interposed between electrode leads or between an electrode lead and an electrode tab and a structure in which a notch part is formed in a film that wraps the electrode leads or the electrode lead and the electrode tab are not suggested.
Korean Patent Application Publication No. 2016-0125920 discloses a pouch-shaped secondary battery including an electrode assembly and a pouch-shaped sheathing member for receiving the electrode assembly, the pouch-shaped sheathing member including a first pouch-shaped sheathing unit and a second pouch-shaped sheathing unit, the first pouch-shaped sheathing unit and the second pouch-shaped sheathing unit being adhered to each other via a sealing unit, wherein the pouch-shaped secondary battery further includes a first electrode lead extending from the electrode assembly, the first electrode lead being attached to the first pouch-shaped sheathing unit, a second electrode lead attached to the second pouch-shaped sheathing unit, the second electrode lead being formed so as to protrude outward from the pouch-shaped sheathing member, a first sealing member interposed between the first electrode lead and the second electrode lead for preventing the first electrode lead and the second electrode lead from contacting each other, and a film-shaped connection member for electrically connecting the first electrode lead and the second electrode lead to each other. However, the invention disclosed in this publication is different from the present invention in that the sealing member is not conductive.
Korean Registered Patent No. 1192077 discloses a secondary battery including an electrode assembly, including a first electrode, a second electrode, and a separator provided between the first electrode and the second electrode, a battery case for receiving the electrode assembly, an electrode terminal electrically connected to the first electrode, and a lead tab extending from the inside of the battery case out of the battery case, the lead tab being electrically connected to the first electrode via the electrode terminal, wherein the lead tab is formed so as to be separated from at least a portion of the electrode terminal such that, when the battery case is deformed in the state in which the lead tab is in contact with the battery case, the lead tab can be electrically disconnected from the first electrode, the secondary battery further includes an adhesive member for adhering the lead tab to the electrode terminal, and the adhesive member is provided with a through-hole, through which the lead tab is electrically connected to the electrode terminal. However, the invention disclosed in this publication is different from the present invention in that an insulative polymer is interposed between electrode leads or between an electrode lead and an electrode tab.
Korean Registered Patent No. 1447064 discloses a battery cell configured such that an electrode assembly having a positive electrode/separator/negative electrode structure is mounted in a receiving unit of a battery case, wherein tabs (electrode tabs) having no active material coated thereon protrude from electrode plates constituting the electrode assembly, an electrode lead for electrically connecting the electrode tabs to each other is located at one end of a stack of the electrode tabs, and the electrode lead is inserted into the electrode tabs at the electrical connection between the electrode tabs and the electrode lead due to the deformation of the electrode lead, whereby physical coupling between the electrode tabs and the electrode lead is achieved. However, a structure in which a conductive polymer is interposed between electrode leads or between an electrode lead and an electrode tab and a structure in which a notch part is formed in a film that wraps the electrode leads or the electrode lead and the electrode tab are not suggested.
That is, a secondary battery including a micro-perforated electrode lead having adhesive properties for short-circuiting a pouch-shaped secondary battery when the pressure in the battery increases or when the volume of the battery increases in an abnormal state of the battery, for example in the case in which the battery is overcharged or in the case in which gas is generated in the battery, has not been suggested.